Prior art apparatus used to retrieve data from mass storage devices utilized hybrid analog/digital circuitry to effectuate the proper timing of control signals to read and write phase encoded data from and to the storage medium. In order for the analog portion to compensate for tolerance in its circuit components, it is necessary that adjustable component elements (such as variable potentiometers and capacitors) be utilized. In addition to requiring that each unit be individually fine tuned for proper performance, which requires additional labor, the prior art devices were not adaptable to automated testing procedures because of the need for analog to digital (A/D) and digital to analog (D/A) converters. Even when D/A and A/D capabilities were available such testing did not usually point out the individual component problem but only pointed to the general analog portion of the device. The instant invention, requiring only digital components, is easily adapted to automatic testing procedures and therefore requires less labor for troubleshooting. As an illustration of the labor savings, it is noted that the phased locked oscillator of U.S. Pat. No. 3,731,220 requires four manual adjustments for each device, the oscillator appearing nine times for reading a nine track recording -- a total of 36 individual adjustments for that device versus zero in the instant invention.